Yup, beautiful aint it!

If you take a large black slug, Arion ater, and stroke it on the back where the rough skin of the 'head' meets the ridged back the slug will dance.

OK so it just rocks from side to side but its the nearest to a dance a slug will ever get!

It only works with the black slugs; interstingly, I've never had any luck getting the orange colour morph of Arion ater to dance only the black ones.

I have no real idea why they do it, the only reason I can think of is it is a defence mechanism, making the slug look bigger than it is and therefore too big for the bird to eat. It works better with the larger ones, again is this because it is a learnt trait or just that there is more body mass to move? Any ideas?

If you show this to a friend you can have them convinced you've hynotised the slug by moving your finger in time to its swaying!

I hesitate to ask this Graham, but how did you discover this remarkable fact?

I would like to say it was by randomly furtling around with slugs, however, I was shown this by a local slug expert around twenty years ago when I first started field teaching.

I can claim the credit, though, for experimenting with the other species and discovering it was only the black ones that dance.

Is it just me, or does anyone else find themselves torn between revulsion and entrancement?